Accelerating rubber with 5-carbalkoxy-4-alkyl-2-thiazolesulfenamides



United States Patent 3,020,266 ACCELERATING RUBBER WITH S-CARBALKOXY- 4-ALKYIL-2-THIAZOLESULFENAMIDES John J. DAmico, Nitro, W. Va., assignor to Monsanto Chemical Company, St. Louis, Mo., a corporation of Delaware No Drawing. Original application Dec. 31, 1956, Ser. No. 631,441, now Patent No. 2,914,535, dated Nov. 24, 1959. Divided and this application Feb. 2, 1959, Ser. No. 795,885

2 Claims. (Cl. 260-795) This invention relates to accelerating vulcanization with 5-carbalkoxy-4-alkyl 2 thiazolesulfenamides represented by the formula '1 R :0 o 0 0 R where R and R represent lower alkylgroups. These compounds possess unusual stability and are excellent accelerators for vulcanization of natural and synthetic diene hydrocarbon rubbers. Heretofore, no stable thiazole sulfenamide had been found. Substitution of one or both the amide hydrogen atoms has been necessary. For example, 4,5-dimethylthiazolesulfenamide decomposes upon standing under ordinary conditions over a one week period whereas the new compounds are stable indefinitely. They may be prepared by oxidative condensation of the mercaptothiazole and ammonia.

To a suitable reactor containing 750 ml. of "concentrated ammonium hydroxide there were added concurrently an aqueous solution comprising 50.8 grams (0.25 mole) of -carbethoxy-4-methyl-Z-thiazolethiol (Levi, Gazz. Chem- Ital., 61, p. 723, 1931), 40.0 grams (0.25 mole) of 25% sodium hydroxide and 100 ml. of water, and 148 ml. (15.1 g./100 ml.) of sodium hypochloritc. The temperature was held at 0-5 C. during the addition which required 90 minutes. The reaction mixture was stirred for one hour longer and 4 grams of sodium sulfite then added to destroy the excess hypochlorite. was collected by filtration, washed with water until free of chloride and air dried at room temperature. The 5- carbethoxy-4-methy1-2-thiazolesulfenamide was obtained in 73.5% yield, M.P. l24l25 C. Analysis gave 13.06% nitrogen and 29.14% sulfur as compared to 12.83% nitrogen and 29.38% sulfur calculated for C- l-I N O S The new compounds are powerful accelerators with strong delayed action properties for butadiene-styrene copolymer rubber, natural rubber and other diene hydro The product p carbon rubbers. As illustrative of the accelerating activity rubber compositions were compounded comprising.

Stock Parts by weight Smoked sheet rubber Carbon black (Philblack O) Zinc nrirle Stearie acid Saturated hydrocarbon softener Sulfur 5-Carbethoxy-4-methyl-2-thiazolesulfenamide cu vuucocao The stocks were vulcanized by heating for various periods of time in a press at 144 C. The modulus, tensile and scorch properties are set forth below:

It is intended to cover all changes and modifications of the examples of the invention herein chosen for purposes of disclosure which do not constitute departures from the spirit and scope of the invention.

This application is a division of Serial No. 631,441, filed on December 31, 1956, now Patent No. 2,914,535.

What is claimed is:

l. The process of vulcanizing rubber selected from the group consisting of natural rubber and butadiene-styrene copolymer rubber which comprises heating the rubber, sulfur and small amount suflicient to accelerate vulcanization of 5-carboloweralkoxy-4-loweralkyl-2-thiazolesulfenamide.

2. The process of vulcanizing rubber selected from the group consisting of natural rubber and butadiene-styrene copolymer rubber which comprises heating the rubber, sulfur and small amount sufficient to accelerate vulcanization of 5-carbethoxy-4-methyl-2-thiazo1esulfenamide.

References Cited in the file of this patent UNITED STATES PATENTS 2,779,809 Carr Jan. 29, 1957 

1. THE PROCESS OF VULCANIZING RUBBER SELECTED FROM THE GROUP CONSISTING OF NATURAL RUBBER AND BUTADIENE-STYRENE COPOLYMER RUBBER WHICH COMPRISES HEATING THE RUBBER, SULFUR AND SMALL AMOUNT SUFFICIENT TO ACCELERATE VULCANIZATION OF 5-CARBOLOWERALKOXY-4-LOWERALKYL-2-THIAZOLESULFENAMIDE. 